Just died!!!!!!!

So I was driving up the highway last Friday at cruising speed, and the 4.0 l XJ just died. I thought it stopped running, so I tried to start in in Neutral, but low and behold, it was barely running. So I pull over in the worst place, and shes dead. The XJ will roll over, and start, but it will not continue to run....
So, does anyone have any ideas????? Sensors?????
See, the thing is that it was running for about 45 minutes without a problem, when it just shut down. Everything seems fine, but it will not stay running!!!
So, if anyone has any ideas, please let me know!!!!
Thanks all!~!!

fuel pump would give these symptoms
also fuel filter
use some starting fluid and see if you can keep her runnin w that if so you have spark and have now narrowed it down

x2.

what year?

If you have EFI, relieve the valve at the fuel rail to see if you have fuel coming out. If not, then its a fuel pump. If you have fuel, then chances are CPS or ignition, etc

you can still have fuel at the rail without having enough voulme/pressure to get the engine running